The blast furnace tuyere is mainly subjected to the high-speed erosion of high-temperature hot air (up to 2000°C), the impact and erosion of slag iron and hot materials, and large thermal stress. In addition, when pulverized coal is injected, the tuyere is also subject to wear by high-speed pulverized coal; when material collapse occurs in the blast furnace, it is also affected by lumpy furnace charges. Therefore, the tuyere refractory materials often suffer damage and air leakage. Blast furnace tuyeres used to use clay bricks or sillimanite bricks, but now silicon nitride-bonded or self-bonded silicon carbide refractory bricks with excellent alkali resistance and high strength are mostly used.
The daily iron throughput of each tap trough of a large blast furnace is approximately 3,000 tons, so the refractory materials of the tap trough are generally required to have good erosion and erosion resistance and thermal shock resistance. In the 1950s, tap trench refractory materials were generally made of clay, carbonized bricks, graphite or coke powder, asphalt, etc., and were pounded. In the 1960s, Al2O3-SiC-C refractory materials for tap troughs were developed, which had excellent spalling and erosion resistance and significantly extended the service life of the tap trough. Since the 1980s, the tap troughs of large blast furnaces have mostly been formed by casting. The raw materials used are mainly fused corundum, silicon carbide, a small amount of metallic silicon powder, aluminum powder and an appropriate amount of coagulant.
The material used in the main trench of large blast furnaces is mainly pure calcium aluminate cement-bound castables. In order to self-flow, the amount of fine powder and water is increased. It is mostly used in blast furnaces with 2 to 3 tapholes; quick-drying agents and coagulants are added to make The resulting castable is called quick-drying castable and is mostly used in blast furnaces with a single taphole or blast furnaces with tight production schedules. The sol-bonded castable developed by Wuhan Iron and Steel Co., Ltd. is a self-cleaning bonded castable. It does not use cement bonding. As the temperature increases, its compressive strength increases and its oxidation resistance is good. The primary iron flow rate of the self-flowing castable in the Wuhan Iron and Steel Co., Ltd. 1513m3 blast furnace exceeds 150,000 tons; the quick-drying castable can be demoulded 1 hour after molding and can be put into use after 2 to 3 hours of rapid baking. The main trench of a 2200m3 blast furnace is used. After 1 to 2 partial repairs, the iron flow rate exceeds 200,000 tons. Ton.
The refractory material of the iron trench does not store molten iron in normal times and will not be soaked by high-temperature molten iron and slag for a long time. Therefore, the damage caused by penetration and erosion is not as serious as that of the main trench. However, the iron ditch is used discontinuously at high temperatures, so the iron ditch refractory materials are required to have good thermal shock resistance. The iron trenches of large blast furnaces often use low-cement bonded castables and no-bake ramming materials. The rapid baking pollution-free ramming material developed by WISCO does not use organic binders, has low moisture content, can be baked quickly, and has achieved satisfactory results.
The taphole has to withstand the erosion and erosion of molten iron and slag as well as the thermal shock generated by tapping iron, so the damage to the refractory material of the taphole is relatively serious. Clay bricks and high alumina bricks were commonly used in the past. Currently, high-performance Al2O3-SiC-C materials are being actively developed. The mud used to block the taphole is called taphole mud, which is generally required to have the following characteristics: good plasticity, adhesion and sintering; no cracks and shrinkage during use; high strength; good corrosion resistance; sintering The rear gun mud is easy to open. Clay clinker, high-aluminum clinker, mullite, silicon carbide, carbon particles and clay raw materials are generally used for gun clay. Large blast furnaces use fused corundum, silicon carbide, sericite, clay, etc. as raw materials, and mix them with water or resin to make water-free or water-free gun clay.